The present invention relates to a milling apparatus, especially a milling machine for crankshafts. Such machines have a base on which two chucks or vises are supported to hold the two ends of the workpiece such as a crankshaft. A milling unit carrying a plurality of milling cutters is movable back and forth on guide means on the machine bed or base toward or away from the workpiece.
Machines of the just described type operate in such a manner that after a crankshaft has been placed into the respective mounting chucks, the milling unit is advanced toward the crankshaft in a so-called immersion movement until the disk milling cutters reach the diameter of the bearing surface of the crankshaft. At this point the milling unit is stopped and the crankshaft is rotated with its chucks. Thus, the milling of the bearing surfaces of the crankshaft is completed when the crankshaft has made one full revolution.
Conventional crankshaft milling machines of the just described type have mainly three drawbacks. First, the milling accuracy of the workpiece is small. Second, the milled surface of the workpiece shows chatter marks. Third, the operational life span of the disk milling cutters is too short.
The just mentioned disadvantages of conventional crankshaft milling machines of the described type are the result of unsatisfactory dynamic characteristics of these machines. Such undesirable dynamic characteristics are inherent in the machine itself because the crankshaft, which as such is relatively flexible, is generally supported in a sufficient manner by special supporting devices.
It is also known to provide machines of the just described type with stop means which limit the feed advance movement of the milling unit and thus the immersion depth of the milling cutters, whereby these stops determine the diameter of the bearing portions of the crankshaft. Such stops have been heretofore arranged close to the machine bed or base, whereby the resulting dimensional precision of the final bearing surface diameters was limited in prior art machines of this type and it was hard to adjust the stops.